This invention relates to a flexible inspection system for use in both industrial and medical applications and, more particularly, to an elongatable, flexible, fiber optic inspection device slidably received in an external tubular guide member.
Elongated inspection devices, particularly such device incorporating flexible fiber optics, are often used to inspect sites which would not normally be visible to the human eye. The jet engine is one type of mechanical structure for which such inspection would be most useful, particularly to inspect the burner cans and the first stage, or high temperature stage, of the engine just behind the burner cans. These are among the components of the engine that are most subject to wear and deterioration. The arrangement of the jet engine's rotor and stator blades, particularly those in the high temperature stage of the engine, presents a most complex geometry which has not been amenable to inspection in the past other than by first disassembling the engine. There has been a need for some form of inspection device which can be placed near the rotor and stator blades, and other important sites within the engine, for the inspection thereof without the laborious task of disabling the engine. The use of this type of instrument would effect a substantial savings in the cost of maintenance of the engines. Savings would result from the man-hours saved by avoiding the disassembly and reassembly of the engine. Additional savings would result from the increase in service time of the engine since the downtime for maintenance would be substantially reduced.
A further appreciation of such tubular inspection devices can be more readily attained by considering those currently in use in the practice of medicine. For instance, a common form of such a device, known as an endoscope, is used for the inspection of the human colon while similarly structured device is used for inspection of the urethra. The endoscope is conventionally used in the diagnosis of tumors and other conditions in the lower gastrointestinal tract. The endoscopic examination involves the physician observing the intestinal wall through an eyepiece in the control head of the instrument. Generally, the endoscope, or colonoscope as it is termed in this procedure, is provided with a source of illumination at its objective end, the end which is placed adjacent the area to be examined, and a bundle of light-transmitting fibers through which an image of the examined area is transmitted back to the eyepiece. The endoscope can further incorporate a channel which provides a washing fluid for application to the site under examination as well as a surgical tip and other features. In other similar procedures the endoscope can be more specifically termed gastroscope and a bronchoscope.
A factor to be considered in the construction of the endoscope for its normal medical use is its flexibility and articulation which permits the objective tip to be directed along the channel of the colon. An endoscope can be made to traverse a considerable distance within the colon providing that any bends in the colon have a sufficiently large radius of curvature to enable the objective end of the endoscope to be readily articulated to follow the course of the colon. Care must be taken, however, to precisely guide the instrument so as not to puncture the colon wall, especially as the device is being inserted.
A problem arises in using presently available flexible devices for the internal inspection of complex articles of manufacture such as interior regions within jet engines. For example, certain compartments within the engine, such as the aforementioned regions within the burner cans and the turbine, are at present effectively inaccessible to viewing by an inspector. Such inaccessibility is the case even with the use of an inspection device such as an endoscope because the articulation of the inspection device requires some sort of guiding surface, such as the interior wall of the colon, to orient and support the inspection device. In contrast to the colon of the human body, a jet engine has an interior characterizied by relatively open spaces and few appropriate supporting surface readily available to guide the objective end of the inspection device. In addition, presently known endoscope designs, even when used for their originally intended purpose, are not easily able to negotiate all colon configurations without substantial risk of puncturing the colon wall.
As a result of recent catastrophic aircraft losses ostensibly caused by faulty internal jet engine structures and components, more frequent borescopic examinations have been mandated. This requires an inspection system which is easily used, which provides an optical image of highest clarity, and which can be readily inserted into the engine, then just as readily removed from the engine. A previously proposed solution to the problem calls for inspecting a number of different aspects of the jet engine and includes inspecting the burner cans arranged in a circular fashion. In order to inspect each aspect of each of the burner cans, the borescope must be inserted through one of two spark plug openings (typically in burner cans numbered seven and four, respectively, of a nine can construction) and then reach the remaining burner cans cans in the circle via the crossover tubes connecting adjacent burner cans.
Currently available devices for performing such an inspection depend upon the combination of a guide tube which contains therein a viewing scope, the distal end of which can be extended from the end of the guide tube once the proper location is found. The purpose of this arrangement is to slip the guide tube in through the spark plug hole and up into the vicinity of the cross over tubes and then extend the viewing scope out of the distal end of the guide tube and into the cross over tube so that the guide tube can be fed into the next burner. Some known mechanisms for extending the viewing scope from the distal end of the guide tube include a scissors type of arrangement whereby the viewing scope is pushed farther into the guide tube from the proximal end thereof.
There are two major problems with the known devices incorporating the scissors arrangement for advancing the viewing scope into the guide tube. The first is that as the viewing scope holder is brought towards the proximal end of the guide tube to push the viewing scope therein, the viewing scope kinks up or arcs and this causes material fatigue of the viewing scope which tends to unravel the viewing scope and have it break apart. The second problem is that an operator of the known devices must use one hand to push the viewing scope holder towards the guide tube base and the other hand to feed the viewing scope tube into the entrance hole of the guide tube base. This is an extremely awkward maneuver and it would be best carried out if the operator had a third hand which would put a varying force on the kink created to make the feeding easier.
Additional problems with the known devices are that the guide tube can only articulate in two directions, i.e. in one plane, which makes it very awkward and time consuming to get the distal end thereof in the proper location for feeding the viewing scope through the crossover tubes. This is generally done by lining up in the plane by which articulation of the distal end thereof is possible and then jumping or jogging the cable around to exactly line it up so that the viewing scope can be located correctly. Finally, the known scopes cannot easily accomplish inspections of the louvered section of the burner can or the first stage stationary vanes and first rotor as they cannot be easily located in the center of the burner can for ease of such inspection.